Abstract
The interface between the N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide (DEME-TFSI) ionic liquid and a gold (111) surface was investigated with time-resolved X-ray reflectivity in order to clarify the dynamics of structural changes of the electric double layer after changing the electrode potential. In the experiment, the potential was switched repeatedly between +1.5 V and −1.5 V every 2 s or every 0.3 s, while measuring the specular X-ray reflectivity. When the potential was switched every 2 s, the time dependence of the reflectivity was different from that of the accumulated charge. This indicates structural relaxation processes that occur on a slower time scale than the acummulation of the charge at the electric double layer.
When the potential was switched every 0.3 s, on the other hand, the reflectivity changes followed the evolution of the charge of the electric double layer within the experimental precision, indicating that slow relaxation processes without charge transfer do not contribute significantly to structural changes at this time scale.
Acknowledgement
The authors thank Dr. K. Hyodo of the Photon Factory for his support on the beamline. The experiment was carried out at beamline AR-NE7A of the Photon Factory under the Photon Factory experimental programs 2011G068 and 2013S001. The research was financially supported by the program `Development of Advanced Measurement and Analysis Systems' of the Japan Science and Technology Agency, and Japan Society for the Promotion of Science (JSPS) KAKENHI, Grant Numbers 23600018, 15K04616, 26287080, 26105008, 25820373, and 15H01044.
©2015 Walter de Gruyter Berlin/Boston